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United States Patent |
5,305,346
|
Ault
|
April 19, 1994
|
Transverse-type laser assembly using induced electrical discharge
excitation and method
Abstract
A transverse-type laser assembly is disclosed herein. This assembly defines
a laser cavity containing a vapor or gaseous substance which lases when
subjected to specific electrical discharge excitation between a pair of
spaced-apart electrodes located within the cavity in order to produce a
source of light. An arrangement located entirely outside the laser cavity
is provided for inducing a voltage across the electrodes within the cavity
sufficient to provide the necessary electrical discharge excitation to
cause a vapor substance between the electrodes to lase.
Inventors:
|
Ault; Earl R. (Livermore, CA)
|
Assignee:
|
The United States of America as represented by the United States (Washington, DC)
|
Appl. No.:
|
117857 |
Filed:
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September 8, 1993 |
Current U.S. Class: |
372/82; 372/83; 372/87 |
Intern'l Class: |
H01S 003/097.1; H01S 003/097.5; H01S 003/227 |
Field of Search: |
372/82,83,87,86
|
References Cited
U.S. Patent Documents
4295103 | Oct., 1981 | Ljudmirsky | 372/82.
|
4593397 | Jun., 1986 | Proud et al. | 372/82.
|
Primary Examiner: Lee; John D.
Assistant Examiner: McNutt; Robert
Attorney, Agent or Firm: Valdes; Miguel A., Gaither; Roger S., Moser; William R.
Goverment Interests
FIELD OF THE INVENTION
The United States Government has rights in this invention pursuant to
Contract No. W-7405-ENG-48 between the United States Department of Energy
and University of California for operation under Lawrence Livermore
National Laboratory.
Claims
What is claimed is:
1. A transverse-type laser assembly, comprising
(a) first means for defining a laser cavity containing a gaseous substance
which lases when subjected to specific electrical discharge excitation,
thereby providing a source of light; and
(b) second means for subjecting said gaseous substance within said laser
cavity to said specific electrical discharge excitation, thereby providing
a source of light; and
(i) first inductive means including a pair of spaced-apart, confronting
electrodes located entirely within said laser cavity such that some of
said gaseous substance is present between said electrodes, and
(ii) second inductive means located entirely outside said laser cavity for
inducing a voltage into said first inductive means and across said
electrodes sufficient to subject the gaseous substance therebetween to
said electrical discharge excitation and thereby cause the gas to lase.
2. A laser assembly according to claim 1 wherein said first means for
defining a laser cavity includes an axially extending tubular arrangement
defining an axially extending laser cavity and wherein said spaced-apart
electrodes are elongated in configuration and extend parallel with one
axis of said laser cavity.
3. A laser assembly according to claim 2 wherein said first inductive means
includes an open ended, electrically conductive inner tube having an
axially extending gap which is located along its entire length and which
is defined by opposite lengthwise ends of the tube, and wherein said
elongated electrodes are respectively connected to and along the length of
said lengthwise ends of said inner tube.
4. A laser assembly according to claim 3 wherein said second inductive
means includes an open-ended, electrically conducting outer tube located
concentrically around said tubular arrangement and said first mentioned
electrically conductive tube, said outer tube having its own axially
extending gap which is located along its entire length and which is
defined by opposite lengthwise ends of said outer tube, said second
inductive means also including means connected across the lengthwise ends
of said outer tube for providing said voltage to be induced into said
inner tube and across said electrodes.
5. A laser assembly according to claim 2 wherein said vapor substance is a
metal vapor.
6. A laser assembly according to claim 5 wherein said tubular arrangement
includes a ceramic tubular member defining said cavity and containing said
inner tube, a layer of insulation around said tube, and a quartz tube
around said insulation.
7. A laser assembly according to claim 5 wherein said metal vapor is copper
vapor.
8. In a transverse-type laser assembly defining a laser cavity containing a
gaseous substance which lases when subjected to specific electrical
discharge excitation between a pair of spaced-apart electrodes located
within said cavity in order to produce a source of light, the improvement
comprising means located entirely outside said laser cavity for inducing a
voltage across said electrodes sufficient to provide said electrical
discharge excitation between said electrodes.
9. In a method operating a transverse-type laser assembly defining a laser
cavity containing a gaseous substance which lases when subjected to
specific electrical discharge excitation between a pair of spaced-apart
electrodes located within said cavity in order to produce a source of
light, the improvement comprising the step of inducing a voltage across
said electrodes sufficient to provide said electrical discharge excitation
between said electrodes from a location entirely outside said laser
cavity.
10. A transverse-type laser assembly, comprising
(a) first means for defining a laser cavity containing a gaseous substance
which lases when subjected to specific electrical discharge excitation,
thereby providing a source of light; and
(b) second means for subjecting said gaseous substance within said laser
cavity to said specific electrical discharge excitation, said second means
including:
(i) first inductive means including a pair of spaced-apart, confronting
electrodes located entirely within said laser cavity such that some of
said gaseous substance is present between said electrodes, and
(ii) second inductive means located entirely outside said laser cavity for
inducing a voltage into said first inductive means and across said
electrodes sufficient to subject the gaseous substance therebetween to
said electrical discharge excitation and thereby cause the gas to lase.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to lasers and more particularly to
an improved transverse-type laser assembly, especially a transverse-type
copper vapor laser suitable for use in what is known as an atomic vapor
laser isotope separation (AVLIS) process.
The fundamental operating concept of a transverse-discharge laser is known
in the art and diagrammatically illustrated in FIG. 1. This figure shows
an axially extending tubular arrangement 10 which defines an axially
extending laser cavity at 12 containing a lasing substance 14, for
example, copper, and a buffer gas (not shown). The overall tubular
arrangement includes, for example, an innermost ceramic tube 16, an
intermediate layer of insulation 18, and an outer quartz tube (not shown).
A pair of spaced-apart, confronting electrodes 20 are disposed within
laser cavity 12, as shown, and a voltage is applied across these
electrodes from a source 22 located outside cavity 12. Source 22 which may
provide a continuous pulsating voltage is physically connected to
electrodes 20 by means of electrically conductive leads 24 extending
through tubular arrangement 10. All of these components and some which
have not been described (but which are not pertinent to this invention)
cooperate with one another (1) so that substance 14 is sufficiently heated
to provide vapor between electrodes 20, as indicated by the arrows 26, and
(2) such that the voltage applied across the electrodes is sufficient to
subject the vapor substance therebetween to an electrical discharge
excitation whereby to cause the vaporous substance to lase. This, in turn,
provides a source of light which is ultimately acted upon to form a laser
beam.
As indicated above, the components described immediately above are only
some of the components making up a known type of transverse-discharge
laser. The other components (not shown) are not pertinent to the present
invention and could be readily provided by those familiar with that type
of laser. These other components include, for example, suitable means
acting on the lasing vapor in order to form the ultimate laser beam. They
may also include means other than electrodes 20 for heating substance 14
in order to produce its vapor 26, although it may be desirable to use only
the electrodes to this end.
The transverse-type laser generally may be an especially suitable laser for
use with copper vapor and the previously recited AVLIS process. This is
because it can be made quite compact and it can be designed to operate
with short voltage pulses and at high repetition rates, desirable features
in the AVLIS process. It could also be attractive in the AVLIS process as
an oscillator and as a means for driving dye master oscillators. However,
one very significant drawback with the known transverse-type laser, as
exemplified in FIG. 1, resides in certain mechanical aspects of this
laser. More specifically, as can be seen in FIG. 1, in order to connect
the electrodes 20 within laser cavity 12 to voltage source 22 outside the
tubular housing 10, it is necessary to provide electrically conductive
leads 24 through the tubular arrangement. Considering the relatively high
temperature within the laser cavity, for example, on the order of
1500.degree. C., the feedthrough points for accommodating the electrical
leads become quite complicated and quite possibly prohibitive.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to
provide a transverse-type laser assembly which does not have the
mechanical drawback recited immediately above. A more specific object of
this invention is to provide a transverse-type laser assembly of the
general type illustrated in FIG. 1 but one which does not require that
electrical conductive leads or other such means be fed through its tubular
housing in order to apply the necessary voltage to its electrodes.
A further object of the present invention is to provide an uncomplicated
and yet reliable way to apply the necessary voltage across the electrodes
within a transverse-type laser in order to produce the desired electrical
discharge excitation therebetween so that the vapor or gaseous substance
between the electrodes will lase.
Still a further object herein is to provide a transverse-type laser
assembly which operates on copper vapor and which is especially suitable
for use in the previously recited AVLIS process.
As will be described in more detail hereinafter, the transverse-type laser
assembly disclosed herein is similar to the assembly illustrated in FIG. 1
to the extent that it includes (1) means for defining a laser cavity
containing a vapor or gaseous substance which lases when subjected to
specific electrical discharge excitation and (2) means including a pair of
spaced-apart, confronting electrodes located in the laser cavity for
subjecting the vapor or gaseous substance therein to specific electrical
discharge excitation. The transverse-type laser assembly disclosed herein
also includes (3) means located outside the laser cavity for applying the
necessary voltage to the electrodes in order to provide the necessary
electrical discharge excitation therebetween. However, there are no
physical connections between the electrodes and the external source of
voltage requiring physical penetration into the laser cavity. Rather, a
first inductive arrangement which includes the electrodes is provided in
the laser cavity and a second inductive arrangement is located outside the
laser cavity. This latter arrangement is designed to induce a voltage into
the first inductive arrangement and across the electrodes sufficient to
subject the vapor or gaseous substance therebetween to the necessary
electric discharge excitation required to cause the vapor to lase. The two
inductors operate as a single turn transformer wherein the excitation
energy supplied externally is coupled to the interior by means of time
varying magnetic fields.
Additional objects, advantages and novel features of the present invention
will be set forth in part in the description that follows, and in part
become apparent to those skilled in the art upon examination of the
following or maybe learned by practice of the invention. The objects and
advantages of the invention may be realized and attained by means of the
instrumentations and combinations which are pointed out in the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings which are incorporated in and form part of this
specification illustrate an embodiment of the invention and, together with
the following description, serve to explain the principles of the
invention. These drawings are as follows:
FIG. 1 is a diagrammatic illustration, partially in perspective view, of
part of a transverse-type laser assembly designed in accordance with the
prior art;
FIG. 2 is a diagrammatic illustration, partially in perspective view, of
part of a transverse-type laser assembly designed in accordance with the
present invention; and
FIG. 3 diagrammatically illustrates an operational feature of the laser
assembly shown in FIG. 2.
DETAILED DESCRIPTION OF THE DRAWINGS
Reference will now be made in detail to the preferred embodiment of the
invention, an example of which is illustrated in the accompanying drawings
(FIGS. 2 and 3). While the invention will be described in conjunction with
that preferred embodiment, it will be understood that it is not intended
to limit the invention to that embodiment. On the contrary, it is intended
to cover alternatives, modifications and equivalents as may be included
within the spirit and scope of the invention as defined by the
accompanying claims.
Turning directly to FIG. 2, a portion of a transverse-type laser assembly
designed in accordance with the present invention is diagrammatically
illustrated, partially in perspective view, and generally indicated by the
reference numeral 30. For reasons of clarity, only those components
necessary to an understanding of the present invention are illustrated.
The other components, that is, those not illustrated, are readily
providable by those with ordinary skill in the art and familiar with
transverse-type lasers generally. The components of the laser which are
illustrated include an axially extending tubular assembly 32 comprising an
innermost ceramic tube 34, an intermediate layer of insulation 36 and an
outer quartz tube 38. This tubular arrangement defines an inner axially
extending laser cavity 40 which contains a vapor or gaseous substance, for
example copper vapor, as indicated by the arrows 42. Assembly 30 also
includes means designed in accordance with this invention for subjecting
the vapor substance 42 within cavity 40 to electrical discharge excitation
sufficient to cause the vapor or gaseous substance to lase and thereby
provide a source of light which is ultimately acted on by other components
of the laser assembly, not shown, for producing a laser beam.
Still referring to FIG. 2, the means for providing the desired electrical
discharge excitation within cavity 40 includes a first generally tubular
inductive member 44 including a pair of spaced-apart, confronting
electrodes 46 located entirely within and along the length of cavity 40
such that some of the vapor or gaseous substance within the cavity is
present between the electrode. A second inductive arrangement generally
indicated at 48 is located entirely outside the laser cavity for inducing
a voltage into the inductive member 44 and across electrodes 46 sufficient
to subject the vapor or gaseous substance therebetween to an electrical
discharge excitation which will cause the vapor to lase. Note that there
are no electrically conductive leads or other physical means passing
through tubular assembly 32. Rather, voltage for electrodes 46 are coupled
to these electrodes by means of induction through the tubular assembly.
Still referring to FIG. 2, in the embodiment illustrated, inductive member
44 is formed from a single sheet of sheetmetal or other suitable
electrically conductive material in the shape of an open-ended tube having
an axially extending gap which is located along its entire length and
which is defined by opposite lengthwise ends that support electrodes 46.
Tubular member 44 is located concentrically around the axis of laser
cavity 40. In a similar manner, inductive arrangement 48, as illustrated,
includes a single sheet of metal or other suitable conductive material
which is formed as an open-ended tube 50 having an axially extending gap
which is located along its entire length and which is defined by opposite
lengthwise ends 52. A pair of spaced-apart confronting connecting flanges
54 connect to and extend out from ends 52 and serve to connect tube 50 to
a source of voltage 58 by means of electrical conductors 56.
Referring to FIG. 3, tubular member 44 and its associated electrodes 46 and
tube 50 and its associated flanges 54 are shown diagrammatically along
with voltage source 58. Note that when the outer tube 50 is connected to
source 58, a primary current ip is caused to pass through the outer tube
which serves as primary or drive coil in the induction process. This in
turn induces corresponding voltage into the tubular member 44 which serves
as secondary coil resulting in a secondary current I.sub.s. The parameters
of the voltages and currents can be readily selected to provide the
appropriate electrical discharge excitation between electrodes 46 in order
to cause vapor or gas therebetween to lase.
In one embodiment of this invention, the laser assembly illustrated in FIG.
2 is contemplated for use as a copper vapor laser in the above recited
AVLIS process. In this regard, liquid copper may be provided within the
lasing cavity, within tubular member 44 in the same manner illustrated in
FIG. 1. This liquid copper can be heated by means of the heat from
electrodes 46 alone or by other supplemental means not shown. Although the
present invention is particularly advantageous for use in the
configuration illustrated, that is, with an axially extending laser cavity
it is to be understood that this invention is not limited to that
particular configuration. For example, the plasma tube 38 may be provided
as the means for containing vapor 42, rather than the quartz tube 34.
This, in turn, would allow the drive coil, that is, tube 50, to be placed
under insulation layer 36. This would provide for greater coupling
efficiency between the outer inductive tube 50 and the inner inductive
tube 44.
The foregoing description of the preferred embodiment of the invention has
been presented for purposes of illustration and description. It is not
intended to be exhaustive or to limit the invention to the precise form
disclosed, and many modifications and variations are possible in light of
the above teaching. The preferred embodiment was chosen and described in
order to best explain the principles of the invention and its practical
applications to thereby enable others skilled in the art to best utilize
the invention and various embodiments and with various modifications are
suited to the particular use contemplated. It is intended that the scope
of the invention be defined only by the claims appended hereto.
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